The present invention relates to an improved circular knitting machine that has a saddle plate with matching cams and sinkers assembled thereon in an inclined manner, and a sinker drum with a concave surface forming a continuous circular ring in the shape of a conical shallow tray to allow the cams and the sinker drum to form a concave and convex surface contact thereby to achieve a smooth match between sinkers and cams.
Conventional circular knitting machines generally include sinkers driven by a cam. The cam has a driving path to move the sinkers to and fro to perform a knitting operation.
The sinker is engaged with a preset driving path as shown in FIG. 1A. During a knitting operation, the lug 62 of the sinker 61 is engaged with the driving path 64 of the cam 63 so that the sinker 61 is moved according to the driving path 64 to perform the knitting operation. The cam 63 is mounted horizontally on the machine deck. The sinker 61 is also mounted horizontally.
Referring to FIGS. 1A and 2, the sinker 61 is located on a sinker drum 60 which rotates at a high speed during knitting operation, and the sinker 61 is driven by the driving path 64 to move reciprocally to and fro rapidly. When the sinker drum 60 rotates at high speed, the sinker 61 is forced outwards due to a centrifugal force, but is retained by the driving path 64 of the cam 63. Meanwhile the lug 62 moves along the driving path 64. The centrifugal force generates a great force on the sinker 61 (indicated by an arrow in FIG. 2). As a result, the lug 62 does not move as smoothly as desired along the driving path 64. The contact surface 66 and contact angle 67 between the driving path 64 and the lug 62 form many stress concentration points. The continuous centrifugal force creates severe friction and wear. As a result, the lifetime of the sinker 61 and the cam 63 significantly decreases.
Moreover, as shown in FIG. 1B the cam 63 is mounted horizontally on the machine deck and the sinker 61 also is mounted horizontally. But the sinker drum 60 is a circular barrel with a plurality of cams 63 mounted thereon adjacent to one another in an annular fashion. There is a gap 65 formed between two neighboring and horizontal cams 63. This resulting connection is not continuous between cams 63. Hence during high speed rotation, interference or interruption can occur with the to and fro reciprocal movements of the sinker 61.
Therefore the object of the invention is to provide an improved circular knitting machine that has a saddle plate with inclined holding surfaces and a sinker drum with an inclined surface so that the matching cams and sinkers are also coupled in an inclined manner. The cams and the sinker drum form a concave and convex arched contact surface so that a gap is less likely to occur. As a result, when the sinker drum rotates, the sinker may be moved along the driving path more smoothly without interference or interruption.
The driving path provided in the invention can also reduce the centrifugal force of the sinker and prevent the lug from hitting the cam. Therefore, the service life of the sinker and cam may increase.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.